1. Field of the Invention
The present invention relates to a wireless network device and a communication method using the wireless network device, and more particularly, to a wireless network device and a communication method using the wireless network device designed to simplify an association process of the device moving over the wireless networks and to enhance mobility of the device.
2. Description of the Related Art
With advancements in communication and network technologies, a wired network environment using wired media such as coaxial or optical cables is evolving into a wireless one using wireless signals in various frequency bands.
In line with the transition from wired to wireless technology, a computing device that contains a wireless interface module, enables mobility, and perform specific functions by processing various information (“a wireless network device”) is being developed and wireless technologies that enable effective communication between wireless devices on a wireless network are emerging.
There are two major architectures of wireless networks: infrastructure and ad-hoc networks.
The infrastructure network contains an access point (AP) 110 as shown in FIG. 1 whereas the ad-hoc network does not require an AP for communication as shown in FIG. 2.
In an infrastructure mode, the AP 110 not only has connectivity to the wired network but also provides communication among wireless network devices within a wireless network. Thus, all data traffic in the infrastructure network is relayed through the AP 110.
In an ad-hoc mode, wireless network devices within a single wireless network can directly communicate with one another without using an AP.
Such ad-hoc mode wireless networks can be further classified into two types.
In one type of network, which is called a “coordinator-based wireless network”, a randomly selected wireless device acts as a coordinator that allocates channel time to other wireless devices within the same wireless network for data transmission, and then the other wireless devices are allowed to transmit data only at the allocated time.
As compared to the coordinator-based wireless network, the other type of network allows all network devices to transmit data at any time desired without using a coordinator.
The coordinator-based wireless network is a single independent coordinator-centered network. When there are multiple coordinator-based wireless networks within a certain area, each network has a unique identifier (ID) to distinguish itself from others.
Thus, while wireless devices can transmit data to and receive data from other network devices during channel time allocated by the coordinator on a coordinator-based network where they belong, they are not allowed to communicate with wireless devices belonging to another coordinator-based network.
For example, in a home network system containing two coordinator-based wireless networks, that is, first and second wireless networks 20 and 30, as shown in FIG. 3, it is assumed that the first wireless network 20 is provided in a living room and the second wireless network 30 is provided in a bedroom, respectively.
If a user desires to watch movies stored on a media server 31 in the bedroom using a portable moving picture player 21 in the living room, then the user cannot watch movies since there is no way to communicate between the first and second wireless networks 20 and 30. Thus, in order to watch the movies, the user has to go to the bedroom.
This problem may arise by restriction on range of radio waves, absence of information on another coordinator-based wireless network, and channel time allocation.
In addition, when the user moves the portable moving picture player 21 from the living room to the bedroom to watch the movie, the portable moving picture player 21 attempts to reassociate with the second wireless network 30 after disassociating from the first wireless network 20. When the portable moving picture player 21 attempts to associate with the second wireless network 30, a coordinator of the second wireless network 30 allocates an identifier to the portable moving picture player 21 for discriminating it among other wireless network devices in the second wireless network 30.
Even though the coordinator allocates different identifiers to the wireless network devices belonging to an identical coordinator-based wireless network, there exist wireless network devices having the same identifier allocated previously in a different coordinator-based wireless network.
As described above, when the wireless network devices having the same identifier previously allocated in the different wireless network exist, the wireless network devices must undergo another association process.
Thus, when a wireless network device moves to different wireless networks, it is necessary for the wireless network device to repeatedly perform association processes, consuming unnecessary time and impeding mobility.
Korean Laid-open Patent Application No. 2004-0004726 proposes a method for reducing delay caused by frequent mobile host authentications in a wireless local area network (WLAN) environment using a reduced authentication token. However, the above-cited reference describes only a method for reducing authentication delay based on the IEEE 802.11x standard. However, there has been no teaching nor suggestion based on the IEEE 802.15.x standard.